The Genetics of Similarity
• Evolution
– A change in gene frequencies within a
population over many generations;
– A mechanism by which genetically influenced
characteristics of a population may change.
– Changes may occur due to mutations or errors
occurring during copying of original DNA
sequence.
– Changes may occur due to natural selection.
Wade/Tavris, (c) 2006, Prentice Hall
Innate Human Characteristics
• Infant reflexes
• Interest in novelty
• Desire to explore and manipulate
objects
• Impulse to play and fool around
• Basic cognitive skills
Wade/Tavris, (c) 2006, Prentice Hall
Innate Capacity for Language
• Language too complex to be learned bit by bit
(Chomsky, 1957, 1980).
• Sentences have surface and deep structures.
– Surface structure
• the way a sentence is spoken
– Deep structure
• how a sentence is to be understood
• To transform surface sentence structures into
deep ones, children must apply rules of
grammar (syntax).
Wade/Tavris, (c) 2006, Prentice Hall
Surface and Deep Structures
Wade/Tavris, (c) 2006, Prentice Hall
Evidence Supporting the LAD
• Children:
– in different cultures go through similar stages of
linguistic development.
– combine words in ways adults never would.
– learn to speak or sign correctly although adults do
not correct syntax.
– not exposed to adult language may invent a
language of their own
• Infants as young as 7 months can derive
simple linguistic rules from a string of sounds.
Wade/Tavris, (c) 2006, Prentice Hall
Evolution and Sexual Strategies
• Due to different kinds of survival and mating
problems, the sexes have evolved differently
in the areas of aggressiveness, physical
dominance, and sexual strategies.
– Males compete with other males for access to
females, and try to inseminate as many females
as possible.
– Females conceive and carry only a limited number
of pregnancies so they choose fewer more
dominant males with good resources and high
status.
Wade/Tavris, (c) 2006, Prentice Hall
Differences in Sexual Strategies
Males
Females
• Want sex more often.
• Are fickle and
promiscuous.
• Drawn to sexual
novelty and even rape
• Are undiscriminating in
partner choice.
• Concerned with
competition and
dominance.
• Want sex less often.
• Are devoted and
faithful.
• Drawn to stability
and security.
• Are cautious and
choosy in partners.
• Less concerned with
competition and
dominance.
Wade/Tavris, (c) 2006, Prentice Hall
Our Human Diversity:
The Case of Intelligence.
• Genes and individual differences.
– Intelligence Quotient (IQ)
• measure of intelligences originally computed by dividing
a person’s mental age by his or her chronological age
and multiplying result by 100.
• now derived from norms provided for standard
intelligence tests.
– The kind of intelligence that produces high IQ
scores is highly heritable.
• .50 for children and adolescents
• .60 -.80 for adults.
Wade/Tavris, (c) 2006, Prentice Hall
Twins and Intelligence
• Intelligence scores of identical twins are
always more highly correlated than those of
fraternal twins.
Wade/Tavris, (c) 2006, Prentice Hall